The present invention generally relates to ink stamping devices useful for making ink impressions on items such as papers, envelopes and cardboard containers. More particularly, the present invention relates to a multi-color stamping device having two or more adjacent pre-inked marking structures containing different color inks, whereby at least one of the marking structures has a non-porous edge for preventing migration of ink between two adjacent marking structures. The present invention also relates to methods and devices for properly assembling a composite marking structure.
Hand stamps having pre-inked marking structures enable a user to create numerous impressions without introducing additional ink into the marking structure. The pre-inked marking structures have microscopic pores that allow the ink initially retained within the marking structure to escape at a controlled rate. One high quality, pre-inked hand stamp is manufactured and sold under the trademark ROYAL MARK by M&R Marking Systems Inc. of Piscataway, N.J. These pre-inked hand stamps include marking structures made using a gel comprising a mixture of thermoplastic resin and ink, which is commonly referred to as a pre-mix.
There are a variety of methods for manufacturing microporous marking structures. In one method, the pre-mix, which includes a desired quantity of ink, is poured into a mold. The mold is then heated in a vulcanizer at a predetermined pressure and temperature for a selected period of time. When the pressure, temperature and time parameters have been satisfied, the marking structure is formed into a microporous slab. The marking structure is then removed from the mold and any excess ink in the structure is removed during a stabilizing process. The marking structure has a resilient microporous network that contains ink, which is released through protruding indicia of a molding when pressed against a surface to be marked.
Another well known method of manufacturing microporous marking structures includes initially forming a microporous structure that does not contain ink. Such microporous marking structures may be manufactured by sintering, salt-leaching or other methods. This type of microporous marking structure is impregnated with ink during a separate procedure which may involve immersing the microporous marking structure in an ink pool, subjecting the microporous marking structure and ink to a vacuum environment or other known methods. With this type of microporous marking structure, it is generally necessary to stabilize the structure, i.e. remove excess ink therefrom, prior to assembly of the marking structure on a hand stamp mount.
Another type of pre-inked stamp uses a microporous foam upon which an image is flash printed. One flash exposure system for manufacturing pre-inked hand stamps is described at M&R Marking System Inc.'s Website at www.mrmarking.com and is provided under the trademark ULTIMARK. In general, the ULTIMARK system comprises a computer controlled flash irradiation device which exposes select areas of foam text plates (i.e. marking structures that have been formulated to be used in pre-inked hand stamps) to a high energy light source for a period of time. A protective film is used to shield certain areas of the microporous foam so that the shielded areas are not exposed to the light source. The brief exposure to light causes the exposed surfaces of the text plate to melt creating substantially non-porous areas at the exterior surfaces of the microporous foam. The unexposed areas remain porous so that the microporous foam can be subsequently used as a marking structure in hand stamps.
In one particular embodiment of the ULTIMARK system, the flash-exposed pre-inked stamps are made by printing or imaging a positive or negative image on a transparent paper or plastic, and then placing that image on a transparent body of typically glass or plastic in between a light source and the microporous foam to be exposed. A clear protective sheet may be placed over the flash exposable microporous material and on top of a transparent indicia medium. An improved process for preparing a microporous material for flash exposure is disclosed in commonly assigned U.S. patent application Ser. No. 10/439,469, filed May 16, 2003, the disclosure of which is incorporated by reference herein.
There have been a number of efforts directed to producing ink stamps capable of printing in two or more colors. For example, U.S. Pat. No. 6,289,806 to Hirano discloses a stamp having an occlusion body with a continuous porous structure that is impregnated with two or more kinds of ink. The occlusion body includes a physical barrier that inhibits mingling of two or more kinds of ink. Although Hirano addresses the issue of color mingling, it requires the use of additional parts in the form of a physical barrier to suppress the mingling of colors.
U.S. Pat. No. 6,047,639 to Shih discloses a stamping set including at least one partition strip that separates an enclosed space into at least two rooms for separating ink of two different colors. Although the '639 patent also addresses the issue of preventing color mingling, it also requires the use of an additional component, i.e. a partition strip.
U.S. Pat. No. 5,601,644 discloses a multi-color ink stamp pad, whereby a thin, aqueous-impermeable film is disposed between the pads for preventing color mingling. Thus, the '644 patent also requires an additional part to prevent mixing of the different colored inks.
There have also been a number of efforts directed to simplifying assembly of hand stamps. For example, U.S. Pat. No. 3,988,987 to Ikura discloses a stamp frame having a vertical interlocking projection on one of its side surfaces, a vertical interlocking groove on the opposite side surface, and a holding member removably mountable over the stamp elements to prevent displacement of the stamp elements relative to one another. Although Ikura applies to ensuring proper assembly of a stamp device, it teaches a registration concept applied to a stamp frame rather than the stamp pad itself. As such, there is nothing in the disclosure indicating a registration concept on the adjacent portions of the marking structure to facilitate the assembly of marking structures on a hand stamp mount.